The disclosure relates to gas turbine engines. More particularly, the disclosure relates to attaching ceramic matrix composite (CMC) ducts in reverse flow combustors.
Ceramic matrix composite (CMC) materials have been proposed for various uses in high temperature regions of gas turbine engines. US Pregrant Publication 2010/0257864 of Prociw et al. (the disclosure of which is incorporated herein in its entirety as if set forth at length) discloses use in duct portions of an annular reverse flow combustor. The annular reverse flow combustor turns the flow by approximately 180 degrees from an upstream portion of the combustor to the inlet of the turbine section. Viewed in axial/radial section, an inlet dome exists at the upstream end of the combustor. Additionally, an outboard portion of the turn is formed by an annular wall known as large exit duct (LED) and an inboard portion of the turn is formed by an annular wall known as a small exit duct (SED). The LED and SED may be formed of CMC. The CMC may be secured to adjacent metallic support structure (e.g., engine case structure). The SED and LED are alternatively referred to via the same acronyms but different names with various combinations of “short” replacing “small”, “long” replacing “large”, and “entry” replacing “exit” (this last change representing the point of view of the turbine rather than the point of view of the upstream portion of the combustor). An outer air inlet ring is positioned between the LED and the OD of the inlet dome. An inner air inlet ring is positioned between the SED and the ID of the inlet dome.
Robustly and efficiently attaching a CMC to the metal presents engineering challenges.